JPH0770447B2 - Method of manufacturing polarizable electrodes - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polarizable electrode used in an electric double layer capacitor, a battery or an electrochromic display.

2. Description of the Related Art Conventional technology will be described by taking the electric double layer capacitor shown in the figure as an example. The structure itself of this electric double layer capacitor is a known technique. A paper-like polarizable electrode is disclosed in
There is one disclosed in Japanese Patent Publication No. 59-93216. This is a paper-like polarizable electrode 1 composed of activated carbon fibers and a binder, on one side of which a conductive layer 2 of aluminum, nickel or the like is formed.
Are formed to face each other through the separator 3, and these are sealed together with the electrolytic solution by the metal case 6, the sealing plate 5, and the gasket 4 that insulates both.

In addition, the one using activated carbon fiber cloth for the polarizable electrode has a large specific surface area of 2500 m ² / g, has few impurities and is suitable for electric double layer capacitors. However, it is much more expensive than activated carbon powder, and if it is not pressurized, the porosity occupies 90% or more (occupies 60% or more even when pressurized), resulting in a large loss in the space. As described above, since there are many spaces, the fibers do not come into contact with each other and the contact resistance increases. Although the activated carbon fiber carrying the activated carbon powder has been devised as described above, the adhesive strength between the two is not sufficient in this structure, and the activated carbon powder is liable to fall off.

Further, there is a polarizable electrode in which activated carbon powder is bound with a fluororesin and held on a current collector. Since this is a fluororesin, the resistance increases.

Problems to be Solved by the Invention In the polarizable electrode having the above-described structure, in the case of the paper-like state, the content of the binder is increased in order to increase the strength, the resistance value is increased, and the impedance is also increased. Moreover, the purity is low and the operating voltage cannot be increased. Further, the activated carbon fiber cloth is low in space efficiency and expensive. Even when activated carbon powder is used, the content of the binder increases and the resistance value increases. When activated carbon powder is supported on activated carbon fibers, the activated carbon powder is likely to fall off.

Means for Solving the Problems In order to solve the above problems, the present invention uses a fibrous phenolic resin as a skeleton to carbonize a structure having a phenolic resin adhered thereon, and activates the activated carbon to obtain an activated carbon structure. It is a method of manufacturing a polarizable electrode.

Operation With the above configuration, it is possible to realize a highly reliable polarizable electrode suitable for rapid charging, while increasing the activated carbon fiber density of the polarizable electrode to reduce the resistance and increase the energy density.

Examples Examples of the present invention will be described below. In addition, the polarizable electrodes according to the manufacturing method of the embodiment of the present invention are used to construct an electric double layer capacitor having the structure shown in FIG.

(Example 1) A novolac-type phenol resin fiber (diameter: 5 to 9 microns) was woven, and a satin-woven resin fiber cloth having a basis weight of 250 g / m ² was used as a skeleton, and this was dipped in an aqueous solution-type resol-type phenol resin. The structure thus obtained is 1
After curing for 60 hours and adhering 60 g of the resol type phenol resin, steam was supplied in a nitrogen gas atmosphere and heated at 1000 ° C. for 20 minutes to carbonize and activate the entire phenol resin. The structure had a thickness of 0.7 mm, carbonization, an activation yield of 36%, and a specific surface area of 2100 m ² / g. This activated carbon structure was punched out to a diameter of 6 mm to form a polarizable electrode, and an aluminum layer was formed on one surface to 200 μm by plasma spraying.

Using this, a coin-type electric double layer capacitor shown in the figure was constructed. As the separator 3, a polypropylene porous membrane having a diameter of 10 mm was used. After the polarizable electrodes 1 were opposed to each other through the separator 3, 1 mol / l propylene carbonate organic electrolytic solution containing tetraethylammonium borofluoride (Et ₄ NBF ₄ ) as an electrolyte was injected and then the casing was sealed and coined. A type capacitor was created. This capacitor was charged at 2.4 V and then discharged at a constant current of 1 mA to obtain a capacity of 0.38 F and an impedance (1 KHz) of 12 Ω. Also, always in an atmosphere of 70 ° C
When 2.4V was applied, the capacity reduction rate after 1000 hours was 3% with respect to the initial capacity. The characteristics of the conventional capacitor using the activated carbon fiber cloth and the paper-like activated carbon fiber as the polarizable electrode were 0.21F and 0.23F, respectively, and the impedance was 21Ω and 35Ω. The capacity of this embodiment is sometimes
In terms of impedance (1KHz), it is particularly superior to conventional ones.

(Example 2) The same phenolic resin cloth as in Example 1 was loaded with a powdery phenolic resin on its skeleton and hot pressed at a temperature of 200 ° C to cure the resin. The supported amount is 55 g. This phenol resin structure is 900
It was heated to 50 ° C. at a heating rate of 50 ° C./hr, carbonized and activated. A polarizable electrode was prepared using the activated carbon thus obtained to prepare an electric double layer capacitor (same as in Example 1), and a capacitance of 0.36 F and an impedance of 14Ω were obtained.

(Example 3) Felt phenolic resin (250 g / m ² ) was used as a skeleton to carry an aqueous phenolic resin (60 g / m ² ) and carbonized and activated in the same manner as in Example 1 to give a specific surface area of 1900 m ² / g. Activated carbon was obtained.
Using this product, a coin-type electric double layer capacitor shown in the figure was prepared and the following characteristics were obtained. That is, the capacitance is 0.36F and the impedance is 12Ω.

(Example 4) A phenol resin chop having a diameter of 5 to 9 microns and a length of 2 to 5 mm and a powdery (10 to 20 microns) phenol resin were used.
The mixture was mixed at a ratio of 60:40 and hot-pressed into pellets at a temperature of 200 ° C to be molded. The porosity is 30% and this molded product is 1000
Activated carbon was obtained at a yield of 40% by carbonizing and activating while supplying steam under a nitrogen gas atmosphere at a heating rate of 100 ° C / hr up to ℃. The specific surface area was 1800 m ² / g. When this activated carbon was used as a polarizable electrode to prepare an electric double layer capacitor by the same material and method as in Example 1, the capacitance was 0.36F and the impedance was 12
Got Ω.

Example 5 A paper-like phenol resin having a thickness of 100 μm was impregnated with 20 wt% of a water-soluble resol-type phenol resin. Subsequent steps were the same as in Example 4 to obtain a paper-like activated carbon having a specific surface area of 1700 m ² / g. When this activated carbon was used as a polarizable electrode to prepare an electric double layer capacitor by the same material and method as in Example 1, the capacity was 0.13 F and the impedance was 14.5 Ω.
Got

(Example 6) An active carbon polarizable electrode similar to that of Example 1 was used as the positive electrode side polarizable electrode, and lithium was occluded in an alloy (Wood alloy) having a Sn: Cd weight ratio of 85:15 as the negative electrode. An electric double layer capacitor was prepared using the electrodes. Also in this embodiment, the other constituent materials are the same as in the first embodiment. LiClO ₄ was used as the electrolyte. This capacitor has a voltage of 3V, 0.78F
Capacity.

The polarizable electrode of the present invention can be widely used not only in the electric double layer capacitor as described above but also in batteries, electrochromic displays and the like.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to obtain a uniform polarizable electrode having a higher energy density, lower resistance, and lower resistance.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electric double layer capacitor using a polarizable electrode according to an embodiment of the present invention. 1 ... Polarizable electrode, 2 ... Current collector, 3 ... Separator,
4 ... Gasket, 5 ... Seal plate, 6 ... Case, 7 ...
… Wood alloy.

Claims (1)

[Claims] 1. A method for producing a polarizable electrode, which comprises a fibrous phenolic resin as a skeleton, and a structure having a phenolic resin attached thereon is carbonized and activated to be activated carbonized to form an activated carbon structure.